Empty promises, their preferred currency

Where to start? Traded my bike for another. They told me they don’t really want to do the deal because there is no market for my bike. They advertised it as a once in a lifetime find and sold it for nearly double what the offered me. The bike I bought from them was immaculate and I am very lucky to get it because it is so well looked after. It has been months to try get them to fix the oil leaks, sensor faults etc. what’s even worse is getting any communication from them on progress etc. never ever again!!!!